Control Scheme

[npf]

All:

I am new to the process industry.I am working on LNG project in the development of P&ID's. I am trying to understand the logic (or undertsand how it is trying to control) for 2 valves HV-1000 and HV-500 marked w/ an arrow in the attachment.
A sequence of operation would be good way to understand.

Your help would be appreciated.

See attachment

Regards,
npf

 

[controlnovice]

The P&ID doesn't indicate very well how the HV-1000 or HV-500 function. The only indication is the HIC block connected to the valve, but no indication of the process variable the valve is trying to control (Level, temperature, pH, pressure, etc.).

The HZSO/HZSC are open/close limit switches. The HY pointing to the solenoid valve is a fail safe interlock from an SIS system.

Nothing at all to indicate what the valve is controlling.

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This is normally the space where people post something insightful.

 

[ilan7]

Each of Those valves need two signals:
One 4-20 ma to the I/P or into the positioner for modulating control of the valve (usually this is the output signal of a controller).
The second signal is an ON/OFF signal to the Solenoid valve which will allow the pneumatic output of the positioner to get to the actuator and make it work.

Regards
ilan

 

[npf]

All:

Thanks for the responses.

Regards,
npf